Technical Field
The invention relates to optical components, touchscreen panels, and display devices.
Background Art
Japanese Patent Application Laid-Open Nos. 06-258634 (Patent Literature 1) and 2012-230390 (Patent Literature 2) disclose display devices that are viewable through polarized sunglasses or the like. The display device of Patent Literature 1 includes a liquid crystal display (LCD) panel, a front-side polarizing plate on the front of the LCD panel, and a phase plate on the front of the polarizing plate. The phase plate is oriented such that its optic axis forms an angle of approximately 35° to 55° with the absorption axis of the front-side polarizing plate. The phase plate is configured to have a retardation in a range of approximately 4,000 nm or larger. Linearly polarized light emitted from the front-side polarizing plate travels through the phase plate to be converted into elliptically polarized light. Hence, the display device is viewable from any direction through polarized sunglasses or the like, without suffering from uneven coloring in the display face.
The display device of Patent Literature 2 includes an LCD panel, a polymer film, and a polarizing plate disposed therebetween. The LCD panel has white light emitting diodes serving as a backlight source. The polymer film has retardation in the range of 3,000 nm to 30,000 nm. The polymer film is oriented such that its slow axis forms an angle of approximately 45° with the absorption axis of the polarizing plate. The white light emitting diodes exhibit an emission spectrum of a similar shape to the envelope curve of the spectrum of transmitted light traveling through the polymer film. This configuration aims to improve visibility of the display device when viewed through polarized sunglasses or the like.